The present invention relates to a method and apparatus for attaching metal members for assembling automotive vehicle structures.
It is known that the manufacture of automotive vehicles often requires that metal members be attached to each other for forming automotive vehicle structures. Friction stir welding is one potential method of attaching metal members. Conventional friction stir welding typically requires a rotating tool to be translated along an interface between surfaces of metal members for softening or melting portions of the members at the interface. In turn, the softened or melted portions intermix and harden to form metallurgical bonds between the members. During a conventional friction stir welding process, however, substantial amounts of liquidized material may be lost or unused forming weaker bonds. Moreover, a conventional stir welding process may require relatively large amounts of time for forming metallurgical bonds. Thus, there is a need for improved techniques, fasteners or both, alternative to conventional friction stir welding for achieving high integrity attachment of a metal members.
The present invention meets these needs by providing an improved method for attaching metal members, with particular utility in the formation of components for an automotive vehicle. The method includes placing the metal members in contact with each other and fastening them with a metal fastener having a central axis. The metal fastener includes an elongated portion having a substantially constant cross-sectional area at any cross-section taken along a length of the elongated portion perpendicular to the axis of the fastener. The elongated portion also includes a topographically varying outer surface. The fastener is driven through the metal sheet and into the metal substrate during rotation of the fastener thereby inducing friction between the fastener and the metal members for locally melting the members to form a flowable material that solidifies for attaching the members, the flowable material and the fastener together.